Many adults discover they can't eat shellfish

Once someone develops an allergy to shrimp, does that mean that person can't eat any shellfish? What exactly are they allergic to?

Once someone develops an allergy to shrimp, does that mean that person canít eat any shellfish? What exactly are they allergic to?

It is possible to be allergic only to crustaceans, the class of shellfish that shrimp belong to, and not to all members of the other class, mollusks, which includes oysters and clams.

But it might not be worth the risk of eating them to find out, allergy experts warn, because of the severity of most shellfish allergies, and because allergic people are usually allergic to both classes.

Allergies to finned fish are also common but do not appear to be linked to shellfish allergies.

In more than half of the people with shellfish allergies, symptoms do not appear until they are adults. Crustacean allergy symptoms are particularly severe, with shrimp, lobster and crab the usual culprits.

All true allergies involve a reaction to a particular protein, called an allergen, and several shellfish allergens have been identified. There are also some shellfish poisons that cause symptoms that resemble allergies.

In the case of shrimp, the major allergen is tropomyosin, which is also found in some mollusks and even in insects and dust mites, according to a review article in the journal Clinical and Translational Allergy.

Most shellfish allergens are proteins that are involved in muscle contraction.

Research on the molecular structure of tropomyosin might eventually lead to a way to desensitize allergic people, scientists say.

In the meantime, the only effective way to manage such an allergy is strict avoidance of even a tiny amount of the suspect shellfish, not just on its own but also as an ingredient in prepared foods and in dyes used for medical tests.

Sufferers usually are prescribed a portable injection device for epinephrine, which can be lifesaving in case of a severe anaphylactic reaction.